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Agronomic Comparison of Nitrogen Fertilizer Practices in Saskatchewan

Thavarajah, D. 2001. M.Sc. Thesis. Dept. Soil Science, University of Saskatchewan, Saskatoon, SK


The widespread adoption of direct seeding-fertilizing in western Canada in recent years has led to the development of new fertilizer placement techniques such as side-row and mid-row banding. The objective of this study was to examine how nitrogen (N) fertilizer rate, form [urea versus anhydrous ammonia (AA)] and placement (side versus mid-row banding) affected yield, protein and crop N recovery in a direct seeding system for three crops (wheat, canola and flax) at four locations in Saskatchewan. Field experiments were conducted at four sites in four Saskatchewan soil-climatic zones: Star City (Moist Black), Indian Head (Black), Scott (Moist Dark Brown) and Swift Current (Brown). Each study site had 14 treatments with four replicates and three different crops. Grain yield, protein content, apparent N use efficiency (NUE), total N uptake and fall soil available N concentrations after harvest were measured. Additionally, a study was conducted at the Star City site in which ion exchange resin membrane probes (PRS™) were used to measure N and P supply rates from fertilizer bands to the seed row from seeding until canola plants emerged. Generally, the rate of N fertilizer had a greater agronomic impact than different N placement methods and forms for all three crops. Maximum yield was generally achieved at the high rate (120 kg N ha -1 ) for wheat and at the medium rate (80 kg N ha-1 ) for canola and at the low rate (40 kg N ha-1 ) for flax. The different N forms and placement methods had relatively small and inconsistent effects on all three crops under better soil moisture conditions as observed at the Star City and Indian Head sites. Under dry spring soil conditions and where soil available N was low, as at the Scott site, side-row band placement was a better method and urea was a better form than anhydrous in terms of yield response and crop N recovery. Under fallow conditions, N placement or form was less important, likely as a result of the high available N in the soil after the fallow period. Among the crops, flax tended to be less responsive to N fertilizer management as compared to wheat and canola. The Indian Head and Star City soils had lower responses to added N fertilizer than the Scott soils, which may reflect greater contribution of available N by mineralization over the growing season. Overall, relative performance of different N forms and placement methods appears to be related to spring soil moisture conditions, as these conditions influenced N fertilizer losses by volatilization and N fertilizer mobility in the soil. In the N supply rate process study, side-row banded urea at the medium N rate (80 kg N ha-1) showed significantly higher available N supply rates to the seed-row than mid-row band placement. Side-row banding may be of benefit when conditions such as low soil moisture restrict root growth and N movement as observed at the Scott site. At high N rates with sensitive crops such as canola, the high supplies could also cause seedling damage. However, as shown in the yield and NUE data, the position of the fertilizer N band in relation to the seed row had relatively less impact on agronomic characteristics than the rate of added N. The largest influence of N fertilizer form and band placement strategy might be anticipated under dry conditions, where lack of moisture may restrict mobility of the N and also enhance losses of N by volatilization.